I'm using Safari 5 (on OSX) and no issue w/ iLok - even though the site says optimized for version 4.
As much as I dislike the dongle, ever since I started using one w/ Pro Tools last year, I must admit that I never had any issue w/ it.
OTOH, I've had authorization/copy protection issues with:
Cakewalk instruments (many times)
IK Multimedia Plug-ins/libraries (many times)
Focusrite plug-ins (twice, now fixed)
Korg instrument plug-ins (2 or 3 times in 1 1/2 month)
Arturia instruments (once)
SSL's Duende Code Meter (once)
If you ask me, the absolute worst type of copy protection is - by far - the soft version of the traditional dongle, like Arturia is using. It is much worst than the actual hardware. But any authorization method can give you issues and they all can cause a significant downtime.
So far, the hardware dongle is the only method that has not let me down at one point or another. I've also been lucky w/ Waves, but I consider the cloud to be similar to other methods already mentioned above which have failed at one time or another for me.